The property across the street is going to be a warehouse. It's part of the lakemont business park. No relation to Carowinds other than proximity.
As for the work at carowinds, there are two stormwater permits on the SC side.
One is for 2018 flyers relocation and listed as a 1 acre job.
The other is for 2019 project alpha which is listed as a 5 acre job.

Screenshot_20180405-234335_Chrome.jpg (360.91KiB)Viewed 3217 times
This picture shows the two areas covered by the stormwater permits.
I don't see how the part next to the road could be related to anything accessible to guests unless the literally did a coaster over the parking lot. My thinking is they are probably going to build a warehouse near the road to free up space in the park.